Karbosguide.com - Module 7a.2

Concepts and terminology, on monitors


The contents:

  • Introduction to displays
  • The common principles of all displays
  • The Pixels
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  • Introduction to displays

    When we talk about screens, there are currently three different types to choose from:

    CRT

    CRT stands for Cathode Ray Tube and is the most the common type of displays. They are found in different technologies, such as Invar and Trinitron.

    Flat panel monitors

    Using LCD (Liquid Crystal Display) technology, the flat panel monitors are light, flat and giving a "softer" displays. TFT is the most expensive display of this type. They are found in better grade laptops, and are available also for use with desktop PCs. In 2001 the prices have dropped significantly. The current price is in excess of $800 for a 17.3" flat panel monitor.

    The flat panel monitors is also called a "soft" screen, since the images appear softer than from Cathode Ray Tubes ...

    Plasma screens

    A very different technology being used to produce large (40" and more) screens. Plasma screens are not covered on these pageCPU'en


    The common principles of all displays

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    The principles in these screen types are quite different, but the screen image design rests on the same concepts:

    Pixels

    The screen image is made of pixels (tiny dots), which are arranged in rows across the screen. A screen image may consists of between 480,000 and 1,920,000 pixels. Here you see the three most common monitor resulutions:

    Refresh rate

    The screen image is "refreshed" many times per second, it "flicker". Refresh rates are measured in Hertz (Hz), which means "times per second". This is not the case using a TFT monitor with digital interface - it does not flicker.

    Color depth

    Each pixel can display a number of different colors. The number of colors, which can be displayed, is called color depth. Color depth is measured in bits (8, 16, or 24 bits).

    Video RAM

    All video cards have some RAM. How much depends on the desired color depth. In the mid 1990s the video cards used to have 1, 2 or 4 MB RAM for normal usage. Today they have 16, 32 or more MB of RAM onboard. This is good for gaming. If you only work with 2D programs like Word and Internet Explorer, you really only need 4 or 8 MB of RAM on your videocard, but it is hard to find so small portions in any cards.

    These concepts are central to the understanding of the video system. Since the CRT screens are still by far the most common, they will form the basis for this review.


    The pixels the basic element in the screen image

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    When you look at a screen image, it actually consists of thousands of tiny dots. If you look close you can spot them:

    Each of these dots is called a pixel . That is a contraction of the term Picture Elements.

    In an ordinary screen, each pixel consists of three colors: Red, green and blue. Thus, there are actually three "sub dots" in each pixel. But they are so small that they "melt" together as one dot:

    The individual pixel or dot then consists of three mini dots, also called trio dot . Some screens do not have round dots, but they work the same way. With the three basic colors, each of which can be assigned with varying intensity, you can create many different colors.


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    To learn more

    Read about video cards in Module 7b .

    Read about sound cards in Module 7c .

    Read about digital sound and music in Module 7d .

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